Poly(acrylates) and poly(itaconates) with poly(alkylene oxide) (PAO) side chains are known in the art. (These polymers will be referred to as "vinyl carboxylic PAO ester polymers". If the alkylene is specified to be ethylene, then "PEO" will be used. see J. M. Cowie and Fergusen, J. Polymer Sci: Polymer Physics Edition, Vol. 23, pp. 2181-2191 (1985); J. M. Cowie and S. H. Cree, Ann. Rev. Phys. Chem., Vol. 40, pp. 85-113, (1989); and Cowie and Martin, Poly. Comm. Vol. 26(10), pg 298, (1985) D. J. Bannister, G. R. Davies, I. M. Ward, J. E. McIntyre, Polymer, vol., 25, pp. 1600-1602, 1984) It is also well-known that mixtures of vinyl carboxylic PEO ester polymers with simple inorganic salts results in materials with modest ionic conductivities. (Cowie and Martin cited above) However, the vinyl carboxylic PEO ester polymers have glass transition temperatures (Tg) ranging from about -60.degree. C. upwards to about 0.degree. C. With such low Tg's the polymers are quite tacky and exhibit very poor mechanical properties which limit their application. For example, if these compositions were to be used as antistatic layers on photographic elements that are rolled up upon themselves, they would be subject to a severe defect known as ferrotyping.
Alpha-alumina particles have been added to PAO (alkylene oxide) to improve its mechanical properties (J. E. Weston and B. C. H. Steele, Solid State Ionics, 1, 75 (1982). The addition of salt is known to increase the Tg's of the etheric acrylate polymers by as much as 86.degree. C., depending upon the salt which is used. Unfortunately, the conductivities of the polymer-salt mixtures are dependent upon the polymer Tg, and decrease dramatically as the Tg is raised. (Cowie and Cree cited above and J. S. Tonge and D. F. Shriver, Polymers for Electronic Applications, J. H. Lai Edit. CRC Press, 1989, p. 157) This is believed to be due to retarded mobility of the ions in the polymer matrix as the glass transition temperature increases.
It would be desirable to produce polymeric composites of vinyl carboxylic PAO ester polymers which have low Tg's but with improved mechanical properties. This would extend the possibilities for using these materials in a variety of applications in which poly(alkylene oxide) units are desirable. High molecular weight PEO is a crystalline polymer which limits its transparency and ability to dissolve salts, and thus its use in, for example, optical applications as well as its use for ionic conductivity. The vinyl carboxylic PEO ester polymers are amorphous but have relatively large amounts of PEO linkages. Composite materials with alkylene oxide units which are amorphous but still have excellent mechanical properties would be highly desirable.
An additional advantage could be obtained if mechanical property improvement could be achieved without increasing the polymer Tg. In this case the addition of small amounts of salts would result in ionic conductive materials with improved mechanical properties. Such materials would be highly desirable for such applications as abrasion-resistant antistatic coatings.
Most antistatic coatings which rely on protonic conductors are sensitive to humidity. At low humidity, the conductivity of such antistatic compositions usually decreases. Antistatic compositions using electronic conductors such as vanadium pentoxide have conductivities that are humidity independent but are difficult to coat. Vanadium pentoxide, for example, must be coated in a ceramic type layer. It would be desirable to produce ionic compositions whose conductivity is less dependent on humidity.
The possible applications of composite materials would be further enhanced if the final composite is also transparent as this offers the possibility to use these materials for overcoats on optical components, for example.